What are the answers to these questions and plz explain?

IThe following information applies to the questions displayed below.] Greg's Bicycle Shop has the following transactions related to its top-selling Mongoose mountain bike for the month of March. Greg's Bicycle Shop uses a periodic inventory system. Cost per Unit Date March 1 March 5 March 9 March 17 March 22 March 27 March 30 Units 20 15 10 Total Cost Beginning inventory Sale ($320 each) Purchase Sale ($370 each) Purchase Sale ($395 each) Purchase $210 $4.200 2.300 2,400 1,820 $10,720 230 240 260 10 12